Charge pumps use a switching process to provide a DC output voltage larger than its DC input voltage. In general, a charge pump will have a capacitor coupled to switches between an input and an output. During one clock half cycle, the charging half cycle, the capacitor couples in parallel to the input so as to charge up to the input voltage. During a second clock cycle, the transfer half cycle, the charged capacitor couples in series with the input voltage so as to provide an output voltage twice the level of the input voltage. This process is illustrated in FIGS. 1a and 1b. In FIG. 1a, the capacitor 5 is arranged in parallel with the input voltage VIN to illustrate the charging half cycle. In FIG. 1b, the charged capacitor 5 is arranged in series with the input voltage to illustrate the transfer half cycle. As seen in FIG. 1b, the positive terminal of the charged capacitor 5 will thus be 2*VIN with respect to ground.
Typical charge pump designs, such as conventional Dickson-type pumps, are suited for supplying capacitive loads; however, the efficiency of such pumps drops dramatically when it is required to supply a DC current Load. One common charge pump application is as peripheral circuitry on flash memories for operations where there are such requirements from pumps. Accordingly, there is a need in the art for charge pumps that achieve higher efficiency when supplying DC loads.